x86/mm: Factor out CR3-building code

Current, the code that assembles a value to load into CR3 is
open-coded everywhere.  Factor it out into helpers build_cr3() and
build_cr3_noflush().

This makes one semantic change: __get_current_cr3_fast() was wrong
on SME systems.  No one noticed because the only caller is in the
VMX code, and there are no CPUs with both SME and VMX.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Lendacky <Thomas.Lendacky@amd.com>
Link: http://lkml.kernel.org/r/ce350cf11e93e2842d14d0b95b0199c7d881f527.1505663533.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 16 insertions, 10 deletions

diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 7ae318c340d9..a999ba6b721f 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -286,6 +286,15 @@ static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
         return __pkru_allows_pkey(vma_pkey(vma), write);
 }
 
+static inline unsigned long build_cr3(struct mm_struct *mm, u16 asid)
+{
+        return __sme_pa(mm->pgd) | asid;
+}
+
+static inline unsigned long build_cr3_noflush(struct mm_struct *mm, u16 asid)
+{
+        return __sme_pa(mm->pgd) | asid | CR3_NOFLUSH;
+}
 
 /*
  * This can be used from process context to figure out what the value of
@@ -296,10 +305,8 @@ static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
  */
 static inline unsigned long __get_current_cr3_fast(void)
 {
-        unsigned long cr3 = __pa(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd);
-
-        if (static_cpu_has(X86_FEATURE_PCID))
-                cr3 |= this_cpu_read(cpu_tlbstate.loaded_mm_asid);
+        unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm),
+                this_cpu_read(cpu_tlbstate.loaded_mm_asid));
 
         /* For now, be very restrictive about when this can be called. */
         VM_WARN_ON(in_nmi() || preemptible());
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 1ab3821f9e26..93fe97cce581 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -126,8 +126,7 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
          * isn't free.
          */
 #ifdef CONFIG_DEBUG_VM
-        if (WARN_ON_ONCE(__read_cr3() !=
-                         (__sme_pa(real_prev->pgd) | prev_asid))) {
+        if (WARN_ON_ONCE(__read_cr3() != build_cr3(real_prev, prev_asid))) {
                 /*
                  * If we were to BUG here, we'd be very likely to kill
                  * the system so hard that we don't see the call trace.
@@ -172,7 +171,7 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
                          */
                         this_cpu_write(cpu_tlbstate.ctxs[prev_asid].tlb_gen,
                                        next_tlb_gen);
-                        write_cr3(__sme_pa(next->pgd) | prev_asid);
+                        write_cr3(build_cr3(next, prev_asid));
                         trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH,
                                         TLB_FLUSH_ALL);
                 }
@@ -216,12 +215,12 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
                 if (need_flush) {
                         this_cpu_write(cpu_tlbstate.ctxs[new_asid].ctx_id, next->context.ctx_id);
                         this_cpu_write(cpu_tlbstate.ctxs[new_asid].tlb_gen, next_tlb_gen);
-                        write_cr3(__sme_pa(next->pgd) | new_asid);
+                        write_cr3(build_cr3(next, new_asid));
                         trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH,
                                         TLB_FLUSH_ALL);
                 } else {
                         /* The new ASID is already up to date. */
-                        write_cr3(__sme_pa(next->pgd) | new_asid | CR3_NOFLUSH);
+                        write_cr3(build_cr3_noflush(next, new_asid));
                         trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, 0);
                 }
 
@@ -265,7 +264,7 @@ void initialize_tlbstate_and_flush(void)
                 !(cr4_read_shadow() & X86_CR4_PCIDE));
 
         /* Force ASID 0 and force a TLB flush. */
-        write_cr3(cr3 & ~CR3_PCID_MASK);
+        write_cr3(build_cr3(mm, 0));
 
         /* Reinitialize tlbstate. */
         this_cpu_write(cpu_tlbstate.loaded_mm_asid, 0);